ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

1aSC23. The role of formant synchrony in the coherence of vowels.

Peter C. Gordon

Erika Manning

Dept. of Psych., Univ. of North Carolina, Chapel Hill, NC 27599-3270

The coherence of vowels as auditory objects was studied by comparing
identification thresholds in noise for synthetic vowel sounds (differing only
in the center frequency of a single formant) to identification thresholds for
the distinctive formant presented in isolation. The bandwidth of the noise
masker was limited so that it only interfered with perception of the
distinctive formant. Thresholds for accurately identifying the vowel sounds
were lower than those for identifying the isolated formant. This demonstrates
that vowel sounds cohere in the sense that unmasked formants reduce the masking
of a formant embedded in noise. The advantage of a complete vowel over an
isolated formant appears to depend on the temporal alignment of the formants.
When the onset of the distinctive formant coincides with the offset of the
other formants, then listeners can still identify the vowel sound in modest
amounts of noise. However, in this case thresholds are not lower for vowel
identifications than for identifications of isolated formants. This indicates
that temporal synchrony plays a basic role in the psychoacoustic coherence of
vowels.